Build a practice portal on this computer only: a tiny website with a login page, a "remember me" tick, and a stock page that shows "Log out" only when logged in.
Then build two things with a browser automation tool such as Playwright: a one-time login that keeps its session in a profile folder inside this working folder, and a check that reuses that folder and says "logged in" or "session expired".
Use only the practice portal and made-up credentials: no real site, no real account. Stop the portal when you are done.
Show me how I check it: the check says expired, then logged in after the login, still logged in in a new run, and expired again after I delete the profile folder.
